High-flexibility steel wire and method of treating same

ABSTRACT

Method of shaping foam metal products to provide accurate fit of such products with surfaces such as ribbed or grooved surfaces of a rigid body of metal, glass, plastic and the like by crushing surface regions of a foam metal blank against the surface to which product is to fit. Crushing operation is carried out by progressively pressing blank against surface, with relative movement between blank and surface in direction of length of ribs or grooves, until, under combined effect of pressure and friction, surface regions of the blank permanently assume shape of surface. Relative movement and heat of friction imparts desirable burnishing and densification of the crushed surface regions of the foam metal product. Method provides low cost procedure for producing scrapers, doctor blades, walls or partitions which must accurately fit against a grooved or ribbed surface even though such surface has irregularly spaced grooves or ribs of nonuniform depth or height.

United States Patent [72] Inventor Hans Geipel, Oberhausen-Sterkrade,

Eckehard Forster, Oberhausen, and Wilfried Heinemann, Dinslaken,

Germany [2]] Appl. No. 826,229 [22] Filed May 20, 1969 [45] Patented June 15, 1971 [73] Assignee Firma Huttenwerk Oberhausen AG,

Oberhausen, Germany Continuation-impart of Ser. No. 675,522, Oct. 16, 1967, and continuationin-part of application Ser. No. 750,642, Aug. 6, 1968 and continuation-in-part of application Ser. No. 805,941, Feb. 17,1969.

[32] Priority May 21, 1968 [33] Germany [31] P 17 58 380.1

[54] HIGH-FLEXIBILITY STEEL WIRE AND METHOD OF TREATING SAME 7 Claims, 7 Drawing Figs.

QUNCKING [5]] Int. Cl B211 21/00 [50] Field of Search 72/364;

700; 140/2; l4l8/l2.4, 12 266/25. 3

[56] References Cited UNITED STATES PATENTS Primary ExuminerLowell A. Larson Attorney-Karl F. Ross ABSTRACT: Steel wire drawn in a multistage rolling mill, with intermediate water cooling just before the last stage, emerges from that stage with a temperature of approximately 800 C. and is rapidly cooled, preferably with the aid of a fluidized bed, to a temperature between about 500 and 550 where transformation of austenite to pearlite takes place, the final phase of this transformation taking place substantially isothermally. This wire, when drawn to a fraction of its original diameter, manifests a microcrystalline structure with distinct lamellate zones and has improved torsional and flexural capacity compared with leadpatented and airpatented wires.

HIGH-FLEXIBILITY STEEL WIRE AND METHOD OF TREATING SAME SPECIFICATION This application is a continuation-in-part of our copending applications Ser. No. 675,522, filed October 16, 1967, now Patent No. 3,525,507; Ser. No. 750,642,filed August 6, 1968, now Patent No. 3,506,468; and Ser. No. 805,941, filed February 17, 1969.

Our present invention relates to a method oftreating steel wire to improve its tensile, flexural and torsional properties.

In making wire of this type, e.g. as required for producing steel cables or coil springs. the conventional practice is to wind the hot wire from the last rolling station into a coil, allowing the coil to cool and thereafter heat-treating the wire in a fused bath, such as molten lead. This type of heat treatment is generally referred to as putcnting. a term which may also be used more broadly for the colling of wire in any medium at a controlled rate from a level above the critical point Ac" (transformation of austenite to ferrite) to a range in which austenite istransformed into pearlite.

ln order to satisfy the usual requirements of ductility, flexibility and tensile as well as torsional strength, the wire so treated should have a predominantly sorbitic crystal structure. Sorbite is a fine-grained variant of pearlite and comes into existence upon transformation of austenitic steel at a temperature of approximately 550 C. If the transformation occurs at a lower level, generally below 500 C., the pearlite crystals are still smaller and form a structure known as bainite. This structure is considerably harder than the sorbite and unsuitable for drawing. If, on the other hand, transformation is allowed to occur at temperatures above the level of substantially 550 C., the pearlite becomes progressively coarser as its crystals are surrounded by a ferrite skeleton; such a wire, typically obtained by patenting in air, has good ductility and torsional strength but does not with stand flexure as well as does wire transformed in a range of about 500 to 550C.

In our above-identified copending applications we have disclosed a method of patenting such a wire in a cooling medium of the fluidized-base type, i.e. a stream of carrier gas with entrained solid particles such as ceramic granules of elevated heat-transfer coefficient (preferably between about 500 and 1000 cal./m. hr. C.). The particles may consist, for example, of magnesia and may range between 0.03 and 0.15 mm. in diameter, with a bulk weight of 1.5 to 5 g./cm. Hydrogen, carbon monoxide or other relatively transformation before its temperature falls below the may serve as the carrier fluid. Though the temperature of the cooling medium (solid particles and carrier gas) may be well below the bainite-formation level of about 500 transformation is completed above that level because the wire is led out of the fluidized bed in a state of incipient transformation before its temperature falls below the 500 C. mark. This method can be applied directly to wire coming hot from a rolling mill and thus represents more economical process for obtaining the desired sorbitic structure with substantial exclusion of bainite.

The general object of ottr present invention is to provide a steel wire of high flexural and torsional endurance, eg for use in coil springs.

:\s more fully set forth in our aforementioned application Ser. No. 075.51.. uusteuitic steel wire with a carbon content between about 0.1 and 0. thy weight) is treated in a manner resulting. independently ofthe type ol'eooling medium employed. in a structure having the desired ductility and strength for the purposes specified above. This is accomplished by immediately cooling the hot-rolled wire at a rapid rate of at least C. per second to a temperature within the austenite/pearlite transformation range. i.e. a temperature lying generally between 500 and 550 C. although its lower and upper boundaries may be around 480 and 580 (1, respectively. The forced-cooling process. which should start not later than about one second after the wire has left the last rolling stage at a minimum temperature of about 800 C, should lower the temperature of the wire to a level below the 608 line of the iron-carbon equilibrium diagram within a few seconds and should be terminated after not more than about 10 seconds from the time of its inception: the 605 line should be penetrated during the first half of that phase, preferably within the first two seconds after discharge ofthe wire from the rolling mill. The final transformation phase may proceed sttbstantially isothermallly over a period of about 10 seconds.

The initial cooling phase (past the: G08 line) may be carried out by quenching in water while the subsequent cooling is performed in a fluidized bed as described above.

A wire so treated has surprisingly high stress resistance along with the necessary ductility allowing it to be drawn to the desired final diameter. Without wishing to commit ourselves to any delinitc theories in explaining these phc uomena. we ascribe them to a freezing of the molecular structttre produced by rolling which may be characterized by a high density oldislocations.

We have found that the treatment of wire by the afore described method results in a sorbitic structure comparable to that realizable, albeit at substantially lower production rates, with a bath of molten lead. Moreover. the treatment according to our invention is faster than patenting in air and tends to suppress the formation of the ferrite skeleton usually associated with air cooling.

After the wire has emerged from the fluidized bed, transformation proceeds to completion under substantially isothermic conditions, i.e. without the use of a cooling medium other than the surrounding atmosphere. To retard the cooling at this stage it is. however, desirable to shield the emerging wire by sheet-metal plates or the like reflecting its thermal radiation. The final cooling, subsequent to transformation, may also take place in air.

In order to stabilize the temperature of the emerging wire within the desired range of approximately 500 to 550 C., we prefer to measure that temperature and to compare it with a predetermined value to compensate for deviations therefrom by a corrective adjustment of the bed temperature and/or of the residence time of the wire in the fluidized bed. To control the temperature of the cooling medium, we prefer to remove particles continuously from the bed and to let them pass through a cooling chamber before returning them to the bed; this recirculation of the particles is best accomplished with the air ofa flow of carrier gas which may itself be recirculated.

We have now found that wire so treated. when observed under the electron microscope, exhibits a structure of distinct lamellate zones, not encountered in conventionally lead'cooled material, which account for a significant part of the cross-sectional area, the lamellae of the several zones extending in different directions while lying substantially parallel to one another within each zone. This lamellate structure may account for the surprising fact that the treated wire according to out invention has both a torsional and a flexural endurance appreciably greater than those of lead-patented wire of like composition and dimensions. Particularly good results are obtained with steels having a carbon content between about 0.5 and 0.7%. by weight, which pass the (E08 line near the 7 0 level so that a workpiece with an initial temperature of 800" to R50" t. can be brought to that level in I to 1 seconds by forced cooling at a rate of 30" to 50" (1 PCI' second.

In accordance with a highly advantageous feattlre of our invention, the rolling of the wire is carried out at temperatures well above the 800 level during one or more stages and is brought to approximately that level, by forced cooling leg. with the aid of a water spray), just before the final rolling stage. This improved technique preserves and even enhances the torsional and flexural endurance of the wire treated in the above-described manner (as disclosed and claimed in our application Ser. No. 805,941) while simplifying the preliminary shaping operation on account of the higher temperatures (up to about 1000" C.) which can be used in the earlier rolling stages. More generally. the preliminary rolling should take place in a range whose lower limit lies substantially 80 above the transformation point AC3, which with a carbon content of 0.5% is approximately at 760 C. whereas the rolling in the last stage (or stages) is carried out at a reduced temperature near that transformation point, i.e. within about 50 thereof.

The wire so treated is cold-drawn, in a manner known per se, so as to undergo a deformation of approximately 80 to 90% in terms of reduction of cross-sectional area, corresponding to a decrease in diameter by a factor of roughly 1.5 to 3.5. The drawn wire exhibits a torsional capacity exceeding that of conventionally lead-patented drawn wire of like dimensions and composition by about 20%, its bending capacity lying by about above that of the conventional wire.

A plant suitable for carrying out the aforedescribed method comprises a conveyor, preferably in the form of an apertured belt, passing through a channel together with the stream of carrier gas and entrained solid particles; the discharge end of the channel is provided with a gate through which the cooled wire may emerge while the particles are retained and form a nearly stationary accumulation around the exiting wire. The hot incoming wire may be deposited on the conveyor in a succession of loops. advantageously with the aid of a transversely oscillating dispenser as disclosed and claimed in our commonly owned application Ser. No. 675,405 filed October 16, 1967, now abandoned.

The invention will now be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a transformation diagram showing the conversion of austenitic steel to sorbite by conventional means and by our present process;

FIG. 2 is a somewhat diagrammatic side-elevational view of a plant for carrying out the process;

FIG. 3 is a fragmentary view similar to FIG. 2, showing a modification;

FIG. 4 represents part of the iron-carbon-equilibn'um diagram, including the G08 line;

FIGS. 5 and 6 are two electron micrographs taken, respectively, of wire treated by the present process and of conventionally lead-patented wire; and

FIG. 7 diagrammatically illustrates the two last stages of a rolling mill supplying the wire to the plant of FIG. 2 or FIG. 3.

In FIG. 1 we have shown at A and B the boundaries of the austenite/pearlite transformation range for a typical steel wire of 5.5 mm. diameter, made from unalloyed steel with a carbon content of 0.5%. Graph e represents an idealized process whereby the wire is rapidly cooled, from a starting temperature of 860 C. attained at the output stage of the rolling mill, to a level of 550 C. which it reaches after 1.5 seconds and where the graph intersects the boundary curve A of the transformation range. After a further interval of about 18.5 seconds. with gradual cooling to a point at or above 500 C., the transformation to sorbite would be completed without the formation of appreciable quantities of bainite. Such as idealized cooling process, e.g. with quenching in water, would be difficult to realize because of the problems of temperature control and appears to be impractical for any but the thinnest wires.

It is widely assumed. even if not established by incontrovertible proof, that the qualities of steel wire especially in regard to flexure are improved by an approximation'of the conditions represented by graph e. This may be accomplished, to a certain extent, by the use of a bath of molten lead (graph 0) which, in order to avoid the formation of bainite, should be maintained at a temperature of about 500 C. so that the curve approaches this level asymptotically; this type of treatment. completed after 20 seconds, does not lend itself to the processing of hot wire coming at relatively high speed from a rolling mill. Conventional air disclosed in our application Ser. No. 805,941 is represented LII by graphs b, c and [1. Graph 12 illustrates the cooling by ceramic granules of the aforedescribed type having a heattransfer coefficient a=600 cal./m. hr. C. as compared with a value a 1180 for the lead bath of graph a. Graphs applies to ceramic particles with a 850. The particle temperature is maintained well below 500 C., yet contact between the particle stream and the wire is terminated at a point p or q, thus after 9 or 6 seconds, respectively, when the wire temperature drops to a level of 520 C. The treatment then continues substantially isothermally for a further period of approximately 20 seconds, to a point r well beyond the intersection of graphs b and c with curve B, whereupon final cooling proceeds in the open air (without any thermal shielding) as indicated by the joint portions b, c of the two graphs. According to graph h, which is illustrative of our present improvement, forced cooling (at a rate of about 40 C. per second) is initiated 1 second after the wire emerges from the rolling mill with a temperature of 800 C., the wire leaving the fluidized bed at a poing s 7 seconds later (thus, at the 8-second mark) after having reached the temperature range between 480 and 580 C., it then remains at a nearly constant temperature, of about 520 C., for approximately 10 seconds before clearing the lower boundary B of the transformation range.

Curve i represents the limiting case of cooling at a rate of 20 C. per second from a starting temperature of 800 C., reached at the exit of the last rolling stage, down to a level of 5 C., within about 10 seconds,followed by substantially isothermal completion of transformation at that level during an interval of slightly less than 15 seconds. The other boundary of the operative region has been partlyshown by a horizontal line j marking the 480 level.

The rapid beginning of forced cooling immediately after rolling, with the wire well within the austenitic range, prevents any reorientation of the stressed grains of the crystalline structure which would otherwise occur at the high workpiece temperature, thereby effectively locking in the strain imparted to the structure by the rolling process.

From the diagram FIG. 4 i t will be noted that'th boundary between austenite and the ferrite/austenite mixture, represented by the line GOS, lies at a level of approximately 750 C. for steel having a carbon content of about 0.6%. In FIG. 1 the G05 line has been indicated at that level and is shown to intersect the curves b, c and h within the first two seconds and at points where the rate of cooling, as represented by the slopes of these curves, is well over 20 C. per second. If the initial cooling is carried out by an air stream or by water, e.g. with the aid of spray nozzles, the transition to a fluidized bed may take place immediately below the GOS line, thus at a temperature of about 700 C.

Reference will now be made to F IG. 2 for a description of a plant in which the process described in connection with FIG. 1 can be performed. The plant comprises a fluidized bed I confined within a tunnel 24, forming an elongated flow channel, to the vicinity of the upper run of an endless conveyor belt 2 which 18 continuously driven by a motor 15 so that a hot wire 3, deposited thereon after leaving the last stage of a hot-rolling mill and preferably after preliminary quenching as incidated in FIG. 1, is transported on a downwardly sloping path from right to left. Wire 3 passes through a guide tube 4 and a continuously rotating dispenser arm 25, driven by a motor 26, whose rotation forms the wire into a succession of loops deposited on the conveyor 2; the dispenser arm 25 may be subject to continuous transverse oscillations at a frequency related to the loop-deposifiori' rate, as described in our copending application Ser. No.

abandoned. A perforatedbase 27within tunnel 24 forms thelower boundary of bed 1 and is connected to outlets of a manifold through which a carrier gas, as indicated by the arrows, is passed at longitudinally spaced locations by way of the intersticed of belt 2 into the space thereabove. The branch conduits of manifold 10 contain respective valves 9 for controlling the amount of gas thus introduced. A further valve 28 controls the input from a COIHPI'QSSQTQILQthCJ' highpressure source, not shown, whereas two other valves 29, 30 determine the proportion in which a portion of the gas is branched off into a conduit 5 into which opens an outlet of a cooling chamber 6, the latter containing a coil 22 traversed by a coolant. Conduit 5 opens into the tunnel 24 in the vicinity of the housing 23 of the dispenser arm 25.

Solid particles entrained by the gas stream accumulate in a pile just ahead of the shutter 8 where the tunnel 24 is formed with a discharge port 7 for these particles. A similar accumulation is formed at the entrance end of the tunnel by means of a stationary plate 31 underlying the upper run of conveyor belt 2 beneath an inlet branch 32 of conduit 5. Port 7 communicates with a further conduit 33 which leads to the top of cooling chamber 6 and which may include means, such as a pump 34, to promote the return of solid particles from the discharge end of tunnel 24 to the cooler. Another conduit 16, provided with a control valve 35, serves as a suction line to exhaust particles from the vicinity of shutter 8 to a separator 18 whence they are returned to cooler 6 via a pipe 21; the spend carrier gas drawn off by line 16, and by a branch 36 thereof extending from the entrance end of the channel, is removed by a pump 17 into a conduit 19 whence it may be discharged by way of a valve 37 to the atmosphere or to the low-pressure side of the compressor delivering fresh gas to valve 28. A bypass 20. controlled by a valve 38, enables the recirculation of some or all or the gas to manifold 10.

A temperature feeler 11 just beyond shutter 8 senses the temperature of the emerging wire loops and feeds this information to a comparator 13 receiving a reference signal fro'rT storage device 12 adjusted to the desired exit temperature (s -e5 9 mpazatq ts qom wbieba necessary, adjusts the speed of motor to vary the residence time of the wire in the fluidized bed 1 in a manner compensating for any deviations of its exit temperature from the preset reference value.

Dispensing arm 25 is, of course, representative of any conventional type of loop depositor including, for example,

devises 9f l styps hpw in U P339158 N s- 3,056,433.

and Re. 26,052. g

The wire 3 exiting from gate 8, thermally shielded against excessive radiant-heat losses by a tube 39 forming an extension of tunnel 24, continues on conveyor 2 in the ambient atmosphere until its transformation has been completed (point r in FIG. 1). Thereafter, it may be air-cooled more rapidly outside the tube 39, by the same or another conveyor or without any conveyor at all, to room temperature.

In FIG. 3, where elements corresponding to those of FIG. 2 have been designated by the same reference numerals with addition of a prime mark, we have shown the temperature sensor 11 disposed ahead of shutter 8. Sensor 11 ascertains the exit temperature of the wire in terms of the temperature of the fluidized bed I at the discharge end of tunnel 24' and, as before, communicates this information to'a controller 14'; the output of this controller, in contradistinction to the previous embodiment, sets a servomotor 4 0 which adjusts a valve 41 to regulate the amount of cooling fluid passing through coil 22 of chamber 6. The system operates otherwise in the same manner as the arrangement of FIG. 2. Naturally, the control systems ll, 11 shown in FIGS. 2 and 3 could also be combined in a single plant.

EXAMPLE I Steel wire containing 0.58% C, 0.38% Mn, 0.24% Si, 0.01% P and 0.02% S (all percentages by weight), balance Fe and usual impurities, is rolled to a diameter of 5.5 mm. at a temperature of 800 C. One second after leaving the last rolling stage, forced cooling of the wire is started, proceeding at an average rate of 40 C. per second to a level of 520 C., this temperature being maintained for l2 seconds while the transformation from gamma. to alpha iron proceeds to completion. After pickling and rustproofing (bonderizing). the wire is drawn without further heat treatment to a diameter of 1.8 mm., this corresponding to a deformation of about 90%.

Wire so drawn exhibited a tensile strength of I kg./mm. and withstood 22 consecutive cycles of flexing and strightening. A cable formed from six strands of seven such wires each was found to have a service life two to four times as long as identical cables made from conventional lead-patented wire.

EXAMPLE [I The procedure of Example I is followed, using a wire with a content of 0.65% C, 0.55% Mn, 0.24% Si, 0.012% P ar d 0.2% S rolle d to the same diameter of 5.5 mm After P n and. bo d s t eat sd awn.wjth utiunl erheat treatment to a diameter of 2.2 mm., this corresponding to a deformation of about EXAMPLE Ill The composition of the steel is 0.66% C, 0.76% Mn, 0.23% Si, 0.019% P and 0.029% S, balance again iron and usual impurities. The rate of cooling between the 800 starting temperature and the traverse of the G05 line, within two seconds after the discharge of the wire from the rolling mill, is 43 C. per second, this rate being substantially maintained to well below the 550 level. The further treatment is the same as in Example ll.

Graph h of FIG. 1, being illustrative of the optimum within the preferred ranges of carbon content (0.5 to 0.7%), initial cooling rate (30 to 50 C.) and terminal transformation temperature (500 to 550 C.), substantially conforms to all the foregoing examples.

Comparative elongation, bending and twist tests performed for wires treated in accordance with our invention (specifically as per Example 111) and for conventionally leadpatented and airpate nt ed wi r es of like composition and similar diameter yielded the following results as to tensile strength and flexibilities:

TABLE 1 Blue wire, nominal diameter 5.5 mm.

(A) Cooling immediately after rolling (Example Ill):

Tensile strength TAB LE 1 Continued (B) Lead Parenting:

Tensile strength Lot No. Diameter kp. kp./mm.

bl 5.60 2900 1 18 5.74 3070 l 19 b2 5.56 2860 I 18 5.69 3030 1 19 Air Patenting:

Tensile strength Lot No. Diameter kp. kp./mm.

TABLEZ Same wire after 84%.deformation, drawn to diameter of It will thus be seen that the deformed wire of Table 2, when previously treated in accordance with our invention. has a tensile strength on the order of 200 kp./mmF, atorsional endurance in terms of up to 40 consecutive cycles of reversing twist (with a length-to-diameter ratio Lzd of 100). and an average flexural endurance in terms of 24 consecutive cycles of alternating bend (about a radius r= 7.5 mm.). This table also shows that our improved wire, after drawing, exceeds the tensile strength of both lead-patented and airpatented wires. compares favorably with both types of conventional wires in flexural capacity. and matches the torsional capacity of the air-patented wire while greatly exceeding that of the lead-patented one. Its construction on rupture is about 50%.

The structure of the drawn wire obtained by Example 111 and deformed in accordance with Table 2. as observed under the electron microscope with a magnification of 4.000zl. has been illustrated in H0. which shows distinct lamellate zones distributed throughout the cross-sectional area of the steel sample; FIG. 6, representing a similar electron micrograph for lead-patented wire subjected to the same drawing process, exhibits only the rudiments of such lamellae at isolated locations.

Coil springs of mm. diameter, 1 10 mm. length and four turns, formed from this wire. showed an axial compression of only 7% after 10.000 alternate cycles of compression and relaxation, compared with a 20% for shortening in the case of identical springs of conventionally lead-patented wire. An appreciable loss of stability occurred only after 60.000 compression cycles, as compared with approximately 40.000 cycles for the conventional spring.

FIG. 7 illustrates the intermediate cooling of the wire 3 during rolling in a mill whose two last stages have been designated 10] and 102. Sprayers 103 direct cooling water upon the hot wire which passes between rollers 101 at a temperature of about 850 C. and arrives at rollers 102 with a reduced temperature of about 800 C.. continuing then toward the guide tube 4 or 4' of F1G.2 or 3.

Tables 1a and 2a, below, list comparative data for wire made of steel with the composition of Example 111 and treated generally in accordance with graph h, with preliminary cooling before the final rolling stage to 800 C. as per FIG. 7. beginning of further cooling within two seconds after the last rolling step to reduce the temperature to about 520 C. at a rate of approximately 40 C. per second, and a residence time of about 12 seconds at the latter level.

TABLE lu Blue wire. nominal diameter 5.5 mm.

Lot No. Tensile strength kp./mm?

a3 1 15 l 14 a4 1 l3 1 15 TABLE 20 Same wire, after 84% deformation as above.

Lot No. Tensile strength No. of bends No. of twists The microstructure of the wire so pretreated is similar to that shown in FlGS. Sand 6.

Strands of such wire may also be twisted into a cable of great flexibility.

We claim: 1. A method of producing wire of high torsional and flexural capacity. comprising the steps of:

rolling austenitic steel wire with a carbon content between substantially 0.3 and 0.9% by weight at a temperature in a range whose lower limit lies substantially 80 C. above the transformation point A0 continuing the rolling in at least one further stage at a reduced temperature higher than said transformation point by up to about 50 C.; subjecting said wire. immediately after rolling, to forced cooling at a rate of at least 20 C. per second. the forced cooling being terminated within a maximum period of substantially l seconds in a temperature range between substantially 490 and 580 C.; maintaining said wire at a substantially constant temperature level within said range for a minimum period of substantially 10 seconds for completion of transformation of austenite to pearlite; and thereafter cold-drawing said wire to a fraction of its initial diameter. 2. A method as defined in claim 1 wherein said carbon content lies between substantially 0.5% and 0.7%.

3. A method as defined in claim 1 wherein the rate of forced cooling is between substantially 30 and 50 C. per second.

4. A method as defined in claim 1 wherein said temperature range lies between substantially 500 and 550 C.

5. A method as defined in claim 1 wherein said fraction lies between substantially [/15 and l/3.5.

6. A method as defined in claim 1 wherein the initial temperature of the rolled wire and the rate of cooling are chosen to bring about a traverse of the: GOS line of the iron-carbon-equilibrium diagram within substantially 2 seconds from the end of rolling.

7. A method as defined in claim I wherein said wire is subjected to forced cooling between said further stage and a preceding rolling stage. 

2. Method in accordance with claim 1 in which said body of rigid material is an endless belt having ribs and grooves formed in a surface of said belt, said ribs and grooves extending parallel with the length of said belt, and wherein said relative sliding movement is effected by driving said belt lengthwise through an endless path while said foam metal body is pressed against the surface of said belt in which said ribs and grooves are formed.
 3. Method in accordance with claim 1 in which said body of rigid material is a cylindrical roll having ribs and grooves formed in the cylindrical surface of said roll, said ribs and grooves extending circumferentially of said roll, and wherein said relative sliding movement is effected by rotating said roll about the cylindrical axis thereof while said foam metal body is pressed against the surface of said roll in which said ribs and grooves are formed.
 4. Method in accordance with claim 1 in which the pressing of sAid one surface of said foam metal body against said surface of said body of rigid material is effected by pressure exerted upon said foam metal body through a rigid backing member which engages said foam metal body over an area at least substantially coextensive with the area of said one surface of said foam metal boey body.
 5. Method in accordance with claim 2 in which the pressing of said one surface of said foam metal body against said surface of said body of rigid material is effected by pressure exerted upon said foam metal body through a rigid backing member which engages said foam metal body over an area at least substantially coextensive with the area of said one surface of said foam metal body.
 6. Method in accordance with claim 3 in which the pressing of said one surface of said foam metal body against said surface of said body of rigid material is effected by pressure exerted upon said foam metal body through a rigid backing member which engages said foam metal body over an area at least substantially coextensive with the area of said one surface of said foam metal body.
 7. Method for shaping regions of a foam metal body adjacent one surface thereof to conform to the shape of a surface of a body of rigid material wherein said last-named surface has formed therein a plurality of parallel ribs and grooves, comprising progressively pressing said one surface of said foam metal body against said surface of said body of rigid material while causing relative sliding movement between said foam metal body and said body of rigid material in a direction parallel with said parallel ribs and grooves, thereby to cause progressive collapse of the foam structure of said foam metal body only in localized regions of said foam metal body adjacent the areas of contact between said one surface of said foam metal body and said ribs and grooves, and continuing said step of progressively pressing until portions of said one surface of said foam metal body come into contact with the bottoms of the grooves in said body of rigid material, thereby forming in said foam metal body a plurality of notches and projections conforming respectively with said ribs and grooves in said body of rrrrrrrriggid material.
 8. Method in accordance with claim 7 wherein said foam metal body having said notches and projections formed therein is taken out of contact with said body of riigid material and a predetermined amount of the foam metal of said foam metal body is then removed from the ends of at least some of said projections to afford a final fit between said foam metal body and said surface of said body of rigid material wherein a space is provided between the ends of those of said projections from which said predetermined amount of foam metal is removed and the bottoms of said grooves corresponding therewith. 